Car cuts off while driving

[Mde36]

Well here's the skinny Got an 88 325 courtesy of ubernasty drove the car all the way home (60 miles) with no problems. I changed the timing belt, idler pully, water pump and gasket, oil and filter, all the belts and hoses, brake fluid, coolant, fuel filter and a new tank of gas. But when I drive it it randomly cuts off sometimes. It doesn't stutter or jerk it just smooth cuts off and I coast to a stop. As soon as Im stopped it starts right back up and drives like nothing happened. Does anyone know what could be causing this?

[thereisnoyun]

my guess is

ECU or CPS

[ubernasty]

wow, thats never happened to me when i drove it... which was a decent amount, about 35 miles every time i took it to school about 20 times.

my 85 325e has been doing the same thing, but only when its really hot out. it did it a couple times last summer on 100 degrees + days. it did it today again. its a tricky problem to diagnose, and i'm looking into it to find out myself right now.

i thought you had a different motor for it anyway?


i'll be following this thread as i am experiencing the same bs.
car drives great any other time, but when its really hot out it just cuts off and stalls out. then i'll stop and restart fine, but as soon as i start giving it throttle it falls on its face again. did it earlier today, let it sit for 15 mins, and it started right up and made it back home about 2 miles. also i drove it all night w/o any problems...

anyone know what this could be because i'm stumped???

[Mde36]

^^ yea the othe motor is out already, Im just waiting on parts (mounts, oil pan, brake booster, harness adapter etc etc etc) to arrive from zionsville. But for now im rollin with the m20. I'm just tryin to keep it running while I need it.

[ubernasty]

yeah, i hear you... i don't have another motor however, so i'm trying to figure out why the same thing is happening to my m20. its strange as hell, every mechanic i've talked to can't come up with a diagnosis.

[StereoInstaller1]

Replace the main relay FIRST.

[jlevie]

This rather sounds like an electrical problem that is taking power to the DME or coil away. One check would be to see if the voltage at the coil, DME power inputs and DME start input are within a tenth of a volt of system voltage as measured at the power block in the engine bay. If one has more voltage drop than that there may be a poor connection in that circuit.

[ubernasty]

^^ would that only happen when its really hot out though but run perfectly fine any other times at night or mild- cold days?

seems like that may make the wiring super hot in the engine bay, making them softer and more flexible which could make the connections more susceptible to becomes loose. but that doesn't really seem what's going on. the car just stalls out under acceleration, pull over for a few minutes... starts right back up, drives fine for a minute or two then does the same thing. (the longer i let it sit, the longer it will go before cutting out again)

-thanks for the help btw

nick

[jlevie]

Now that's a better description of the problem than in your original post. Based on the latest post I'd add the fuel pump and/or relay to list of suspects.

[ubernasty]

Now that's a better description of the problem than in your original post. Based on the latest post I'd add the fuel pump and/or relay to list of suspects.

that still doesn't answer the mind-boggling question of why it only happens when its really hot out however... so frustrating. i drove about 75 miles today w/o any problems whatsoever, and it was 80 degrees all day. (having problems with 90 degrees + days. and the car is not overheating btw)

i'm about to offer a paypal reward to whoever can provide correct diagnosis to this. :D

[BlUe E30]

hey so im having this problem also i was wondering if you ever figured it out?

[Rion]

Having the same problem, Seems my fuel cuts out, except I don't have to pull over I just tun the key off and back on and it "push starts its self" in 5th.. It does it on Hotter more Humid days I have noticed. Hasn't left me stranded yet, but (knock on wood) I'd like to get the problem sorted out. The fuel pump is new as are the pulse sensors which went out months ago. Timing Belt, water pump, Tune up all in the last 3 months.

I'm going to try the fuel pump relay first, Then I am lost after that.

[Kristeun]

Had this problem as well. turned out to be a faulty ECU, or maybe the MarkD chip in it.

[Adiabatic]

nth-ing the electrical problem diagnosis. Next hot day backprobe power to the DME and/or signal from ignition control circuits (crank pos sensor, flywheel sensor, cam pos sensor, distributor gear sensor, whatever an M20 has) and see if any drop off suddenly when the problem repeats. I'd bet money on ignition control, but thats just because I've seen it happen before, albeit on a different vehicle. After eliminating those possibilities I'd backprobe the fuel pump after the relay or swap out DMEs.

[Slangbox]

Damnit... today it hit 105, which is a record for my area, and my car did the same thing. FML.